You see this kind of behavior in BBM—Blackberry Messenger. Unfortunately, that’s stuck on the Blackberry platform—tied to a sinking ship in my opinion. GroupMe has a chance to be BBM for the rest of us, but also to be an open platform that other interesting group functionality can be built on top of—sending casual invites, starting a flashmob, group buying, quick conferencing (via voice, too!).
Charlie O’Donnell (on First Round’s recent investment in GroupMe)